The American Cancer Society recommends beginning colorectal cancer screening earlier for people with a family history of the disease. (Getty Images)

On the whole, colorectal cancer incidence and death rates have been going down for decades. “We’ve made tremendous advances in the treatment for colon cancer to the present day,” says Dr. Wafik El-Deiry, deputy director for translational research and co-leader of the molecular therapeutic program at Fox Chase Cancer Center in Philadelphia.

Improvements in screening have led to earlier detection and more effective treatment of colon and rectal cancers. Tests like the colonoscopy can find polyps, or abnormal tissue growths. While most of these growths on the lining of the colon (or large intestine) or the rectum are harmless, some develop into cancer over time. When they’re found in the early going, though, these polyps can usually be safely removed.

Yet despite these advances and declining rates of colorectal cancer overall, there’s a counter trend that has been troubling oncologists: While the majority of people who develop colorectal cancer are older, research finds that incidence has been increasing in people younger than 55 since at least the mid-1990s. And a recent study shows colorectal cancer death rates have been creeping up in people 20 to 54 years of age; after declining from 6.3 deaths per 100,000 people in 1970 to 3.9 deaths in 2004, deaths have increased 1 percent annually to 4.3 per 100,000 individuals in 2014.

The study, published last month as a research letter (an abbreviated report) in the Journal of the American Medical Association, found the increase was limited to white individuals. Broken out by age in this group, the colorectal cancer death rate increased 1.9 percent for those aged 40 to 49 years, 1.6 percent for those 30 to 39 and 0.9 percent for people 50 to 54 years of age from 2005 to 2014, according to the research.

“It’s a small increase,” says Rebecca Siegel, an epidemiologist and strategic director of surveillance information services at the American Cancer Society, who led the research. “But it does strongly suggest that the increase in incidence rates is real and not just an artifact of more colonoscopy use.”

But it's not clear what’s driving the increase and why it’s confined to whites. The differences can’t be explained, for example, by rising rates of obesity that can make it more likely a person might develop colorectal cancer. “Disparate racial patterns conflict with trends in major CRC risk factors like obesity, which are similar in white and black individuals,” the researchers note.

“There’s something that’s going on that’s disturbing, and it needs to be explained and understood,” El-Deiry says. Experts say there’s likely multiple reasons for the trend. “It’s probably many factors – not one factor – that may have contributed,” says Dr. David Lieberman, chief of the division of gastroenterology and professor of medicine at Oregon Health and Science University in Portland. “But it’s clearly an important trend, and one that’s going to need further investigation.”

Despite the remaining questions, the latest research findings highlight the need for vigilance when it comes to colorectal cancer, not just among older people, but for those who are under 50. It's at age 50 when the ACS recommends people of average risk for colorectal cancer begin getting screened, such as with a colonoscopy or flexible sigmoidoscopy – another test that finds polyps.

The ACS recommends beginning colorectal cancer screening earlier for people at increased risk based on their family history. For example, a person who has a first-degree relative – a parent or sibling – who was diagnosed with colorectal cancer, should start getting screened at an age 10 years younger than the earliest diagnosis of an immediate family member, or at age 40, whichever comes first. “So if your father got colon cancer at 40, you should start getting screened at 30,” explains Dr. Kurt Melstrom, colorectal surgeon at City of Hope, a clinical research hospital in Duarte, California.

Experts say early screening may also be recommended for people whose immediate family members were found to have polyps – particularly if a first-degree relative had a large polyp removed or had several polyps. “It’s something to think about, definitely,” Melstrom says.

Even in the absence of a history of colon cancer, you shouldn’t ignore potential warning signs or symptoms. “If patients are having symptoms that are related to the colon – and the predominant symptom is going to be rectal bleeding, so bleeding from the rectum with bowel movements – that should be reported to their physicians as well,” Lieberman says.

Other symptoms include abnormal abdominal cramping or abdominal pains, which can’t be otherwise explained. Another change you might prefer to keep to yourself: If your poop starts to become a lot more fragmented, hard to get out or very thin, Melstrom suggests talking with your doctor about it. “Of course, all those symptoms are also quite vague, so I would not start to lose sleep over that, as the majority of the time that actually will not be a cancer,” he says. But experts emphasize people who are younger and middle-aged shouldn’t just shrug these things off either, or assume the problem is something like hemorrhoids, since colorectal cancer is more common in older adults. “See your primary care doctor and have them evaluate it,” Melstrom says. “They will refer you to a gastroenterologist to get a colonoscopy if they think it’s appropriate.”

Along with screening and paying attention to possible signs or symptoms, experts recommend making lifestyle changes to lower risk. That includes exercising, shedding excess weight, and not eating a lot of processed red meat – like ham and hot dogs – which has been linked to a higher risk of developing colon cancer. “What I would recommend is that we stay [as] active as possible, eat a nice healthy diet – not an excessive amount of red meat and … processed meat,” Melstrom says.

Research has also shown there’s a link between diabetes and colon cancer. So clinicians recommend making similar lifestyle improvements to lower the risk of developing diabetes, and for those who have it, managing the chronic disease appropriately. The bottom line, experts say, is to be proactive to reduce the toll of colorectal cancer – whether you’re young or old.